Optical: systems and elements – Holographic system or element – Having particular recording medium
Reexamination Certificate
2001-07-18
2004-05-18
Juba, Jr., John (Department: 2872)
Optical: systems and elements
Holographic system or element
Having particular recording medium
C359S023000, C359S030000, C359S032000
Reexamination Certificate
active
06738170
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for reproducing a 2- or 3-dimensional image from a hologram or a holographic stereogram on which two- or three-dimensional image data is recorded.
2. Description of the Related Art
A holographic stereogram is prepared by recording a number of rectangular or dot-shaped element holograms on one hologram-recording medium. The element holograms are original images that have been obtained by photographing an object, sequentially from different points of observation.
A holographic stereogram containing parallax data concerning only the horizontal direction, for example, is prepared as is illustrated in FIG.
1
. First, an object
100
is photographed from different observation points that lie in the same horizontal plane. A number of original images
101
a
-
101
e
of the object
100
are thereby obtained. Then, the original images
101
a
-
101
e
, which are rectangular element holograms, are sequentially recorded on a hologram-recording medium
102
.
The holographic stereogram records image data representing rectangular element holograms that have been obtained by photographing an object, sequentially from different observation points that lie in the same horizontal plane. When an observer looks at the holographic stereogram, the two 2-dimensional images his left eye and right eye receive, respectively, are different a little. The observer therefore perceives parallax and sees a 3-dimensional image.
An ordinary hologram is spaced from an illumination light source for reproducing a 3-dimensional image. A large space is required to reproduce the 3-dimensional image. To reproduce the 3-dimensional image in optimal conditions, the hologram and the light source need to have a particular positional relationship. This holds true of a holographic stereogram that consists of a plurality of element holograms.
If the hologram and the illumination light source are combined, no space is required for illumination. This helps to reduce the size of the apparatus for reproducing 3-dimensional images. In addition, a 3-dimensional image can always be reproduced in the best possible conditions because the hologram and the illumination light source have a fixed positional relation. A 3-dimensional image may be reproduced in such conditions from a so-called “edge-lit hologram.” A recording medium bonded to a transparent light-introducing block is used to reproduce a 3-dimensional image from an edge-lit hologram.
A transmitting hologram of edge-lit type, from which a 3-dimensional image can be reproduced, is prepared as is illustrated in FIG.
2
. To be more specific, a hologram-recording medium
111
is bonded to one surface
110
a
of a transparent light-introducing block
110
. The light-introducing block
110
is made of transparent material such as glass or plastic and has an appropriate thickness. In most cases, the medium
111
is bonded with index-matching liquid (not shown) to the light-introducing block
110
. This prevents total reflection at the surface
110
a
of the block
110
. Body light
114
from an object
113
is applied from the opposing surface
110
b
of the light-introducing block
110
to the hologram-recording medium
111
. Reference light
115
is simultaneously applied from one end
110
c
of the block
110
to hologram-recording medium
111
. A transmitting hologram of edge-lit type is thereby prepared.
To reproduce an image from the transmitting hologram of edge-lit type, thus prepared, the hologram-recording medium is bonded to a light-introducing block made of, for example, glass. More precisely, as shown in
FIG. 3
, a hologram
121
is bonded with index-matching liquid (not shown) to one surface
120
a
of a light-introducing block
120
. Image-reproducing light
123
is applied from one end
120
b
of the block
120
to the hologram
121
. The hologram
121
diffracts the light passing through it. The light
124
diffracted forms a reproduced image
125
, which is observed by an observer
126
.
As shown in
FIG. 3
, the image-reproducing light
123
is incident on the one end
120
b
of the block
120
at angle of 60°. Since the light
123
is thus applied to the hologram
121
through the light-introducing block
120
, it is possible to prevent surface reflection at the interface between the hologram
121
and air. The larger the angle of incidence, the more readily the surface reflection can be prevented. In view of this it is considered that a compact apparatus can reproduce an image from the edge-lit hologram.
The hologram
121
and the light-introducing block
120
are bonded as shown in FIG.
3
. The resultant unit is inevitably large, which is inconvenient in view of transportation and storage.
As pointed out above, the image-reproducing light
123
is incident on the one end
120
b
of the block
120
at an angle of 60°. The hologram
121
may have a length L of 30 mm and the one surface
120
a
of the block
120
may have a length that is at least nearly equal to the length L. In this case, the light-introducing block
120
needs to be at least 17.3 mm thick.
A number of edge-lit holograms are therefore inconvenient in view of transportation and storage. This is because, each edge-lit hologram is bonded to a light-introducing block that is 17.3 mm thick. That is, each edge-lit hologram must be transported and stored, together with such a long block.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing. An object of the invention is to provide an image-reproducing apparatus that is smaller and lighter than the conventional apparatus that uses a light-introducing block to reproduce an image from an edge-lit hologram. The apparatus can therefore be easy to transport and store. The invention can provide an image-reproducing method, too, which uses no light-introducing blocks to reproduce images.
To achieve the object, an image-reproducing apparatus according to the invention comprises a hologram or a holographic stereogram and an optical member bonded, at its rear surface, to the hologram or holographic stereogram. The optical member has parallel prisms on the front surface. Illumination light is applied to the front surface of the optical member. The illumination light interferes with light diffracted while travelling through the hologram or holographic stereogram. An image is thereby reproduced from the hologram or holographic stereogram that records a 2- or 3-dimensional image. Each prism has an incidence surface, to which the illumination light is applied at right angles.
In the image-reproducing apparatus, the illumination light is applied to an interface between the optical member and the hologram or holographic stereogram, at a fixed incidence angle falling within a specific range, thereby to suppress surface reflection of the illumination light at the interface. More precisely, the fixed incidence angle ranges from 60° to 85°, with respect to a normal to the interface.
In the image-reproducing apparatus, the hologram or holographic stereogram and the optical member bonded thereto may be bent, forming a hollow cylinder, the inner surface of which is defined by the front surface of the optical member. In this case, the illumination light is applied to an inner surface of the hollow cylinder, thereby reproducing a 2- or 3-dimensional image from the hologram or holographic stereogram. Thus, the apparatus can reproduce an image from a hollow cylindrical hologram of edge-lit type.
In the image-reproducing apparatus, the illumination light is applied to an interface between the optical member and the hologram or holographic stereogram, at a fixed incidence angle falling within a specific range, thereby to suppress surface reflection of the illumination light at the interface. More precisely, the fixed incidence angle range from 60° to 85°, with respect to a normal to the interface.
In the image-reproducing apparatus, the hologram or holographic stereogram and the optical member bonded thereto may be bent, forming a
Kihara Nobuhiro
Shirakura Akira
Jr. John Juba
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
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